Ludlum Measurements 334A, Operation Manual

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Model 334A Operations Manual
Ludlum Measurements, Inc 18 January 2021
Flow Calibration
The Model 334A sample flow rate is estimated by monitoring the pump’s electrical current.
Flow calibration is necessary to insure that the Model 334A program is correctly monitoring
and converting the pump current into a flow. This relationship is not linear. As a result, a
three-point flow calibration is used, with validation at a fourth flow rate.
Flow Calibration is also an elevation-dependent function, and thus is required before putting
the unit into service.
Setting Up the Apparatus
To begin the flow calibration, first gather the appropriate equipment for the procedure:

Volumetric Digital Flowmeter (a Rotameter will work as well)

Tygon tubing

Flow restriction device (a clamp or needle valve)

Flow Calibration Aid (included with Model 334A, 1 per order)
Create the testing apparatus by attaching the flow restriction device to the Tygon tubing on
the side of the digital flowmeter opposite the unit, and attaching the flow calibration aid to the
end of the Tygon tubing on the other side. Mate the Flow Calibration Aid with the filter
holder, making sure the edge covers the O-rings, like pictured.
NOTE: Ensure that the variable flow restriction does not completely cut off the airflow
to the pump. The pump is not designed to operate at zero flow and the high vacuum
could damage the pump diaphragm. Do not allow the pump to run below 3LPM for
more than a few minutes.